Are these certificates exclusively for ELB and CloudFront? Does anyone see a way to download a certificate for manual installation on a server (EC2 or otherwise)?

https://docs.aws.amazon.com/acm/latest/userguide/setup-websi...

> Currently, ACM Certificates are associated with Elastic Load Balancing load balancers or Amazon CloudFront distributions. Although you install your website on an Amazon EC2 instance, you do not deploy an ACM Certificate there. Instead, deploy the ACM Certificate on your Elastic Load Balancing load balancer or on your CloudFront distribution.

Ideally ACM certificate issuance and deployment would be two separate things, and this would be a general-purpose CA, which just happens to have integrated deployment tools for ELB and CloudFront.